you are pretty close. i think the issue looks to me to be one of neuromuscular control. i can see how your pelvis tucks under at the bottom. the answer is to… not let it. to learn how you need to hold yourself. for me it is imaginging myself ‘sitting into’ my hip flexors.
slow down your descent. one… two… three… three and a half. maybe even four. you should feel your hip flexors stretch out as you descend. it isn’t supposed to feel entirely comfortable. it should feel like work.
if you can’t feel when your pelvis starts to tuck then try looking side on to a mirror. don’t be afraid to pause in the as low as you can go without pelvic tuck position. hold it there. then try and push it a bit deeper. a little light bouncing. learn how it feels to hold your pelvis securely in position then push depth.
some people find holding a weight out front (dumbbell or kettlebell) helps them push themselves down lower into their hip flexors, too.
seems to me you are on the right track. couple more sessions and you should have it…
x2 on this.
I had/have the exact same problem as you. Bad posterior pelvic tilt at and below parallel. Last winter I strained my low back from years of squatting without pelvic control and have been working ever since to fix it. At the time I was squatting low bar, with flat heels.
For a while after I hurt myself I tried high bar squats until I kept hurting more and more, and then front squats until I kept hurting more and more. I was stubborn, and didn’t want to drop the weights I was using and basically start over from scratch.
This summer I discovered how to actively do what alexus described: maintaining pelvic neutral as I descend into the squat (it is all about neuromuscular control). It took a lot of effort at first. I felt like I was fighting tension in my posterior hips and glutes. I went back to squatting in my weightlifting shoes (elevated heels), high bar, and I always start my squat workouts with a dynamic warmup and foam rolling/self myofascial release for my glutes and piriformis. Before I hurt myself I was squatting in the low 400s. When I started rebuilding my squat I didn’t go over 135 for a few weeks, and have yet to squat over 295 since. It’s slow, frustrating work, but it is worth it. My back hasn’t felt this good in a very long time.